Elsevier

Electrochimica Acta

Volume 52, Issue 9, 15 February 2007, Pages 3280-3285
Electrochimica Acta

Electrochemical properties of TiP2O7 and LiTi2(PO4)3 as anode material for lithium ion battery with aqueous solution electrolyte

https://doi.org/10.1016/j.electacta.2006.10.010Get rights and content

Abstract

Some polyanionic compounds, e.g. TiP2O7 and LiTi2(PO4)3 with 3D framework structure were proposed to be used as anodes of lithium ion battery with aqueous electrolyte. The cyclic voltammetry properties TiP2O7 and LiTi2(PO4)3 suggested that Li-ion de/intercalation reaction can occur without serious hydrogen evolution in 5 M LiNO3 aqueous solution. The TiP2O7 and LiTi2(PO4)3 give capacities of about 80 mAh/g between potentials of −0.50 V and 0 V (versus SHE) and 90 mAh/g between −0.65 V and −0.10 V (versus SHE), respectively. A test cell consisting of TiP2O7/5 M LiNO3/LiMn2O4 delivers approximately 42 mAh/g (weight of cathode and anode) at average voltage of 1.40 V, and LiTi2(PO4)3/5 M LiNO3/LiMn2O4 delivers approximately 45 mAh/g at average voltage of 1.50 V. Both as-assembled cells suffered from short cycle life. The capacity fading may be related to deterioration of anode material.

Introduction

Lithium ion battery with aqueous solution electrolyte have many advantages such as low cost, easy performance, intrinsic safety and environmental friendly and intrigued many researchers since it has being suggested [1], [2], [3], [4], [5], [6]. This type of battery composes of lithium ion host compounds as electrode materials and aqueous solution as electrolyte. Selection of intercalation materials which de/intercalates Li ions at an appropriate potential is a key factor for the performance of the aqueous battery cell because the stability window of aqueous solution electrolyte is much smaller than non-aqueous electrolyte. There are many compounds with flat charge/discharge curves can be used as cathode materials, such as LiMn2O4, LiCoO2, LiCo0.19Ni0.81O2, LiNi1/3Mn1/3Co1/3O2 and so on [1], [2], [4], [6], [7]. But only a few compounds with flat charge/discharge plateau and proper redox potential being selected as anode was reported [1], [2], [8]. Thus, studies on anode material having somewhat proper redox potential and flat charge/discharge plateau are very important.

Polyanionic compounds with 3D framework structure were fully studied as cathode of lithium battery over the last decades due to quick lithium ion diffusion, stable structure, easy preparation, low cost and so on [9], [10], [11], [12], [13], [14]. However, few reports on electrochemical properties of these compounds in aqueous media were found. Many polyanionic compounds with certain redox potentials looked promising as anode materials for Li-ion battery with aqueous electrolyte and some of them are summarized in Table 1 [9], [12].

In this paper the electrochemical properties of pyrophosphate TiP2O7 and NASICON-type LiTi2(PO4)3 as anode materials in a lithium ion battery with 5 M LiNO3 aqueous electrolyte will be reported due to their lower Li-ion intercalation/deintercalation potentials, which can fully use the stability window of the aqueous electrolyte. The possible reason of capacity fading of the test cells will be discussed.

Section snippets

Experimental

The preparation of TiP2O7 and LiTi2(PO4)3 was based on the scheme described by Sébastien Patoux [11]. For TiP2O7, the mixture of TiO2 and NH4H2PO4 were progressively heated to 1273 K with intermittent grinding sequences. For preparation of LiTi2(PO4)3, TiO2 and NH4H2PO4 and LiH2PO4 precursors were mixed and heated to 573 K at a slow heating rate (2 K/min) to evaporate H2O and NH3, then to 873 K (24 h), and finally to 1273 K (48 h). The cathode material LiMn2O4 was commercial available supplied by

Cyclic voltammetry of TiP2O7 and LiTi2(PO4)3 electrodes

The cyclic voltammograms of TiP2O7 and LiTi2(PO4)3 were recorded at room temperature with Pt sheet as counter electrode and saturated calomel as reference electrode. Fig. 1a shows the CV performance of TiP2O7 in 5 M LiNO3. It can be seen that a pair of Li-ion intercalation and deintercalation peaks can be observed at −0.38 V and −0.26 V (versus SHE), respectively. The hydrogen evolution peak shifts below −0.60 V (versus SHE) due to the over potential effect of the electrodes. Fig. 1b displays the

Conclusion

In this study, aqueous lithium ion cells composed of TiP2O7 or LiTi2(PO4)3 as anodes, LiMn2O4 as cathode and 5 M LiNO3 aqueous solution as electrolyte have been fabricated. The TiP2O7/LiMn2O4 cell delivers about 42 mAh/g at an average voltage of 1.40 and LiTi2(PO4)3/LiMn2O4 cell delivers 45 mAh/g capacity at an average voltage of 1.50 V. Both cells have flat charge and discharge curves, which improve the feasibility of lithium ion battery with aqueous electrolyte in application. While the given

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